The exemplary embodiments relate to a piezoelectric oscillator and an electronic device, especially a piezoelectric oscillator that is available to input data into a programmable piezoelectric oscillator and a temperature compensated piezoelectric oscillator, as well as an electronic device that is mounted with the above piezoelectric oscillator inside.
A temperature compensated piezoelectric oscillator that is mounted, inside a package, with an electronic part having a control function, such as a temperature compensating function, a PLL function, etc., as well as a programmable piezoelectric oscillator, are required to rewrite the data (information) of the electronic part from outside of the package according to need. Therefore, a terminal to write data for controlling the behavior of the electronic part needs to be provided outside the package that configures the oscillator.
A related art method writes data into an electronic part with a terminal that is provided on the back surface of a package. This terminal is provided in addition to a basic function terminal (mounting terminal) that mounts the piezoelectric oscillator on an electronic device, etc. However, a piezoelectric oscillator that is configured with a data writing terminal on the back surface of a package is subject to the following problems. First, since the number of terminals to be provided within a specified area is increasing, the surface area of a mounting terminal for mounting a piezoelectric oscillator on a substrate needs to be reduced. However, the reduction of the surface area of a mounting terminal is limited in terms of mounting strength and conduction between the terminal and the mounting substrate. Second, in the case where the data stored in the electronic part needs to be rewritten due to a change of specification, etc., occurring after mounting the piezoelectric oscillator on a substrate, the data stored in the electronic part cannot be rewritten unless the piezoelectric oscillator is removed from the substrate.
Another piezoelectric oscillator addresses or solves the above by placing a data writing terminal on the side of a package. For example, a piezoelectric oscillator according to a related art example is described below. The piezoelectric oscillator according to the related art example has a package configured by laminating ceramic substrates, a piezoelectric resonator element and an IC chip being mounted on the substrates. Further, an external terminal for writing control data into the IC chip is provided on the side of the package. The package is described in detail below.
The piezoelectric oscillator has a package in which spaces are formed, each one being formed above and below the laminated substrate, which serves as a partition, for the purpose of mounting either the piezoelectric resonator element or the IC chip. In the package having the above configuration, the laminated substrate includes four layers and the external terminal to write data into the IC chip is provided on the periphery (periphery in the longitudinal direction of the substrate) of the two substrate layers sandwiched between the top and the bottom layers. With such a configuration, it is envisioned there will be no or substantially no data loss or data alteration due to the short circuit between the external terminal for data writing and the mounting terminal, or a contact between the external terminal and a pattern formed on the mounting substrate of an electronic device, ect. For example, see Japanese Unexamined Patent Publication No. 2000-77943.
With the piezoelectric oscillator according to the related art example, the data on the IC chip can be rewritten, even after the piezoelectric oscillator is mounted on a substrate and the chance of the short circuit with the mounting terminal and the pattern placed on the mounting substrate of an electronic device, etc., will be reduced. However, the related art structure is still subject to other problems. Since the piezoelectric oscillator according to the related art example has a larger number of terminals to be provided outside the package, the wiring inside and outside the package becomes complicated. Further, the data on the IC chip is rewritten by contacting a probe to the external terminal for data writing through a socket, etc. However, making a precise contact between the probe and the external terminal provided on the side of the package is difficult, and therefore the process yield rate may decrease because of the incapability in data writing due to poor contact. Furthermore, since the external terminal for data writing is placed on the side of the package and close to the mounting terminal, the solder between the mounting terminal on the piezoelectric oscillator and the mounting pattern on the substrate may cause a short circuit with the terminal on the side, leading to a malfunction of the piezoelectric oscillator. In addition, if the piezoelectric oscillator according to the above related art example is mounted on a substrate on which electronic parts are densely mounted, an electric signal, etc., may be added at a contact to other electronic parts, etc. due to the closeness with other electronic parts, etc. and cause an alteration of IC chip data.